Field of the Invention
The present invention relates to wireless communications, and more particularly, to a data transmission method and apparatus for a half-duplex device in a frequency division duplex (FDD) system.
Related Art
3rd generation partnership project (3GPP) long term evolution (LTE) evolved from a universal mobile telecommunications system (UMTS) is introduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink, and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink. In recent years, there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) evolved from the 3GPP LTE.
A communication channel between a base station (BS) and a user equipment (UE) is roughly divided into a downlink (DL) channel directed from the BS to the UE and an uplink (UL) channel directed from the UE to the BS.
A method of transmitting data in a 3GPP LTE and LTE-A system employs a frequency division duplex (FDD) scheme and a time division duplex (TDD) scheme. In the FDD scheme, a UL transmission and a DL transmission are achieved simultaneously while occupying different frequency bands. In the TDD scheme, the UL transmission and the DL transmission are achieved at different times while occupying the same frequency band.
In order for the UE to simultaneously perform the UL transmission and the DL transmission, a full-duplex capability is required. Comparing with a full-duplex device, a UE which cannot simultaneously perform the UL transmission and the DL transmission is called a half-duplex device. The half-duplex device advantageously has a lower hardware complexity and is cheaper than the full-duplex device. In particular, like a machine type communication (MTC) device, in a case where transmission data and reception data are different in size, and the transmission data is significantly greater in size than the reception data, the half-duplex device is cost effective.
However, it is assumed that a BS and a UE basically have the full-duplex capability in the FDD scheme of the 3GPP LTE and LTE-A system, and the BS can schedule the UE to simultaneously perform a UL transmission and a DL reception at a specific time. In the above case, the half-duplex device has to select one of the UL transmission and the DL reception while giving up the other transmission. Accordingly, a data transmission method for the half-duplex device is required.